The present invention relates to a method and to a device for protecting and arming fuses in a projectile.
Projectile fuses must satisfy high safety requirements and, in compliance with standards (such as STANAG 4187, MIL-STD-1316E), must include safety devices physically separated from one another. In their storage and transport state, they may not have any stored energy that could lead to premature ignition and/or to charging thereof or to partial release of safety devices. The necessary ignition energy is therefore made available only during launching; from WO 00/31497, inter alia, a mortar fuse having a wind-driven wheel is known, which drives a generator and charges up a battery that is chemically activated only during launching.
The disadvantage with such a system is the necessary storage of battery acid, which sets limits to the storage properties of the ignition system. The individual elements arranged at the front end, such as a wind-driven wheel, acid container, battery cells, generator and ignition electronics with timer, and special impact detectors, adversely affect system safety due to the interfaces and components required for signal transmission.
In projectiles, a shock resulting from launch (mechanical pulse) is used for safety device release, or as a preliminary stage to the armed setting. Cf.
EP-A1-0 156 763, (corresponding to U.S. Pat. No. 4,637,311) which has a high-energy electromagnetic ignition system. In the case of spin-stabilized projectiles, the spin build-up during launch can likewise be used for safety device release and as source of energy.
When employing projectiles, especially mortar grenades, it has repeatedly been demonstrated that conventional percussion fuses do not react quickly enough, that, for example, ignition is effected only after a distance to the target has already been covered, and that most commercially available fuses do not react at all on impact with soft targets. Both of these circumstances can lead to undesirable duds that are difficult to find. A delayed ignition can also reduce the effect at the target, since propagation of the shock waves of the active charge is disrupted or even partially shielded by the target itself.
The object of the present invention is therefore to produce an ignition method and an ignition device for projectile fuses that, high system safety and without complicated electrical and/or electronic features, reacts rapidly on impact and also responds to soft targets. The device should also function reliably even when the angle of impact is acute and on impact with water surfaces.
The device should also be adaptable within wide limits to existing ammunition bodies and be suitable both for mechanical fuses equipped with striking pins and for conventional electrical fuses.
The foregoing and other objects are achieved by the features of the method of the present invention in which a striking or ignition pin is displaced relative to the projectile in a direction opposite to raw pressure from a first position into a second, armed position. Upon impact, the pin initiates ignition by rearward displacement to a third position.
A percussion fuse constructed in accordance with the invention can achieve response times of less than 250 ps and achieve optimum effect at a target even when used in a high-velocity projectile.
The term xe2x80x9cstriking pinxe2x80x9d refers to constructions with a percussion fuse, while the term xe2x80x9cignition pinxe2x80x9d relates to mechanically triggered electrical fuses. The ignition pin used in those ignition devices consequently has only an electrical switching function. In both variants, the construction of the striking pin and ignition pin respectively is similar; only the initiation of the ignition is, in a manner known per se, different.
In accordance with the invention, and viewed in the direction of launching, the striking pin or ignition pin is preferably located in a rear, protected position safeguarded against external influences and is displaced relative to the projectile by and opposite to the ram pressure acting on the head of the projectile during normal launching, forward into an armed setting.
This is especially advantageous as regards safe practice measures; if the projectile is accidentally dropped or improperly handled, ignition cannot be initiated since the ram pressure necessary for moving the striking pin or ignition pin is not present. In addition, long pin displacement paths can be achieved, which increases the overall safety of the system.
The ignition chain can therefore be constructed as desired and as conventionally known; likewise the supply thereof with ignition energy may be as generally known.
The use of ram pressure to displace the striking pin or ignition pin allows diverse structural options. For example, the dynamic pressure can be used pneumatically and/or hydraulically directly to reverse the direction of action thereof; gears and moving parts operable by the dynamic pressure are likewise possible for that purpose.
Mechanical conversion of a rotary movement into a linear movement is especially reliable and capable of being used at any time. By means of an impeller mounted on the striking pin or ignition pin, the latter experiences a rotary movement. If part of the striking pin or ignition pin is provided with an external thread and inserted in a threaded bushing (internal screw thread), after the ram pressure has acted on the impeller the pin will screw itself into the forward armed setting.
Advantageously, the impeller may be arranged behind a front-end central inlet opening and its hub and/or the leading end region of the striking pin or ignition pin matched to the inlet opening so that the forward end position of the impeller closes the inlet opening. Mechanical overload of the pin and/or of the threaded bushing can consequently be prevented and interference with the operating sequence can be avoided.
On impact of the projectile on the target, the impeller and the part containing the inlet opening act as actuating elements for the striking pin or ignition pin. Surface pressure occurring at impact even with soft ground or water is sufficient to displace the pin reliably into a third position initiating ignition. For this purpose, the fit of the threaded bush in its locating bore described as a so-called sliding fit has proved successful, the displacement path of the bush being mechanically limited in the direction of launching.
By means of a double-mass catch known per se, release of a rotor determining safety after a projectile has left a gun barrel can be adapted to the launching characteristic of the projectile and this can be monitored.
A further arming mass, which is subjected to the launch acceleration, is able, in the course of its displacement, to turn a tensioning shaft and hence exert a torque on the rotor by way of a spring connected therewith.
By means of an additional locking part located on the arming mass, the impeller of the turbine can move forward and at the instant of launching effects positive blocking.
It has proved especially worthwhile to safeguard the ignition device by a protective cap, which engages in the manner of a bayonet closure in a rotatable front part. By means of an additional release lug, rotation of the front part can be used to operate a further arming mass catch.
Especially reliable is the engagement of the catch in the displacement path of the arming mass, which generates the spring tension required for rotation of the rotor. In practice, this means that even on a dive from great height, no torque is exerted on the rotor.
Pivoting of the rotor about an angle at center of 120xc2x0 required for complete arming, and hence for ignition, ensures maximum safety, and this notwithstanding a compact construction of the ignition device.
A spring-loaded ball that acts on the threaded bushing of the turbine/ignition pin unit enables the resistance to displacement to be adjusted so that neither heavy rain nor snow nor hail can cause premature initiation of ignition.